1. Field of the Invention
The present invention relates to a leaching method of rare-earth metals using a hydrochloric acid from a manganese nodule.
2. Description of the Related Art
A deep-sea floor manganese nodule is a marine mineral resource, which is endowed at a deep-sea floor of the Pacific Ocean, the Indian Ocean, etc., and contains a great amount of copper, nickel, cobalt and manganese. When developing the deep-sea floor manganese nodule, a smelting technology, which is a process for extracting, separating and collecting valuable metals form the manganese nodule, is an important part which accounts for at least 50% of overall investments in facilities and at least 60% of overall investments in operating costs. A method of smelting the manganese nodule can be classified into a reduction smelting-wet leaching method, a roasting-leaching method and a direct leaching method, and among these methods, the reduction smelting-leaching method, which uses both of dry and wet smelting methods, can easily process and recycle smelting residues and does not use excess amounts of chemicals, is evaluated as an emerging process.
A process of the reduction smelting-leaching method of the manganese nodule includes two steps. First, in step one, the reduction smelting method is used to separate the manganese nodule into a slag, which includes manganese, aluminum, silica, an alkali metal and a portion of iron of the manganese nodule, and a metal alloy, which includes nickel, copper, cobalt and iron of the manganese nodule. The alloy has a poor solubility and is not easily crushed, so sulfur is added to produce a matte. In step two, the matte is dissolved by using an inorganic acid and a solvent extraction method is used to separate the dissolved matte into each metal, then an electrowinning method is used to obtain a final product of a metal or a metallic compound. For typical technologies for leaching the valuable metal from the matte, there are a high temperature high pressure sulfuric acid leaching method and a chlorine gas leaching method. The high temperature high pressure sulfuric acid leaching method uses an autoclave and a sulfuric acid as a leaching reagent, and the matte is reacted in a temperature of 120 to 180° C. and 5 to 10 atmospheric pressure for 1 to 4 hours. However, this method requires a high priced leaching apparatus having corrosion resistant, high temperature resistant and high pressure resistant properties, and requires excessive energy to maintain the leaching solution at a high temperature.
As related arts, there is Korean Registered Patent No. 10-1069964 (Published on Oct. 4, 2011), which discloses a method of manufacturing a valuable metal compound from a manganese nodule.